My prior U.S. Pat. No. 4,760,614 discloses a device consisting of an elongated tube adapted to replace a portion of the piping system. The tube has a through bore with a gate valve along with passageways paralleling the bore and extending from above and below the bore, respectively, to a valve alternatively and selectively connecting the passageways to a supply of pressure fluid so that the pressure fluid may be introduced into the bore of the tubular member either above or below the gate valve.
The device of my earlier patent is not entirely satisfactory because the mounting of the device in a pipe system requires the replacement of a substantial length of piping in the system with the patented device, and for proper operation of the device, it was necessary to coordinate operation of the gate valve with the operation of the three-way valve for controlling the pressure fluid.